Defect inspection method

Abstract

To provide a defect inspection method capable of estimating the size of a smaller projection defect.SOLUTION: A defect inspection method includes: a silicon nitride film formation process of forming a silicon nitride film of 1 to 4 nm in film thickness on a substrate so as to increase the detection size of a projection defect present on a top surface of the substrate; a detection process of detecting the size of the projection part enlarged and formed on a surface of the silicon nitride film on the projection defect after the silicon nitride film formation process by a surface inspection device; and a defect size estimation process of estimating the size of the projection defect before the silicon nitride film formation from the size of the projection part detected in the detection process and the relation between a previously set film thickness of the silicon nitride film and an enlargement quantity of the detection size.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for inspecting defects on a substrate.

Background Art

[0002] Defects present on the surface of a substrate typified by a semiconductor substrate cause device failures. Therefore, with the progress of miniaturization due to the sophistication of devices in recent years, reduction and evaluation of defects have become more important. Defects present on the substrate surface are mainly detected by a particle counter known as a typical surface inspection device. The particle counter inspects the substrate surface by irradiating light onto the substrate surface and detecting scattered light caused by protruding defects (also referred to as particles) present on the substrate surface. The intensity of the scattered light varies depending on the size, shape, composition, etc. of the particles. For example, the larger the particle, the greater the scattered light intensity. Also, in the particle counter, the detected size can be calculated based on the scattered light intensity and the scattered light intensity for each size of the standard particles. That is, the larger the scattered light intensity, the larger the detected size. In order to detect particles with a small detected size, it is necessary to measure with a particle counter for a long time. Also, in the case of particles with a very small scattered light intensity, it cannot be distinguished from the scattered light caused by the roughness (haze) of the substrate surface, so it cannot be detected.

[0003] Patent Document 1 discloses that in order to detect minute particles that cannot be directly detected by a particle counter, by forming a silicon nitride film (hereinafter simply also referred to as a nitride film), the size is made larger than the original particles.

[0004] In this technique, by forming a nitride film, a bulge occurs in the nitride film with minute particles as nuclei. Therefore, by measuring the substrate with a particle counter after forming the nitride film, particle measurement can be performed with high sensitivity. The film thickness at that time is set as film thickness ≧ (inspection device detection sensitivity - defect size) × safety factor, and the safety factor is 100% or more. Here, the detection sensitivity is also referred to as the measurement sensitivity.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] When forming a CVD film such as a nitride film on a substrate, if there are convex protrusions on the substrate, CVD films are formed around them based on these protrusions, and the size of the convex protrusions increases. In particular, since the nitride film has a high refractive index, it can be detected with an even larger size.

[0007] This phenomenon is called the lens effect and is a common phenomenon. However, since CVD films are not formed uniformly, the roughness after the formation of the CVD film generally becomes worse than the roughness of the substrate before the formation of the CVD film. Therefore, when the CVD film is formed thickly, the haze due to roughness deteriorates, and the detection sensitivity of the particle counter decreases.

[0008] However, Patent Document 1 only focuses on the increase in the defect size due to the formation of the CVD film and does not consider the decrease in sensitivity due to haze.

[0009] Also, when only focusing on the expansion of the defect size due to the formation of the CVD film, the particle size can be expected to expand to 19 nm, which is the general measurement sensitivity, due to the formation of a 50-nm CVD film only for particles larger than 12 nm before the formation of the CVD film. That is, particles of 12 nm or less cannot be detected by the formation of a 50-nm CVD film.

[0010] In recent years, the performance of particle counters has improved, and particles of 12 nm or less can be measured without forming a CVD film. The detection sensitivity for the minimum size of this highly sensitive particle counter is 10.6 nm. In this case, when a CVD film is formed by the conventional method, a phenomenon occurs in which the detection sensitivity deteriorates due to the influence of haze. Therefore, when measuring minute protrusion defects with a highly sensitive particle counter, it is more sensitive to measure without forming a nitride film, and the limit (minimum sensitivity) is 10.6 nm.

[0011] As described above, with the further advancement of device miniaturization due to the future higher performance of devices, it is desirable to examine smaller protrusion defects. However, conventionally, there has been a problem that there is no inspection method capable of detecting protrusion defects smaller than 10.6 nm.

[0012] The present invention has been made to solve the above problems, and an object thereof is to provide a defect inspection method capable of estimating the size of smaller protrusion defects.

Means for Solving the Problems

[0013] In order to solve the above problems, the defect inspection method of the present invention includes a silicon nitride film forming step of forming a silicon nitride film having a thickness of 1 to 4 nm on the substrate in order to enlarge the detection size of protrusion defects existing on the surface of the substrate, a detection step of detecting the size of the protrusion formed by enlarging on the surface of the silicon nitride film on the protrusion defect after the silicon nitride film forming step with a surface inspection device, a defect size estimation step of estimating the size of the protrusion defect before the formation of the silicon nitride film from the relationship between the size of the protrusion detected in the detection step, the thickness of the silicon nitride film set in advance, and the amount of enlargement of the detection size, and a defect inspection method including the above steps.

[0014] With such a defect inspection method, by forming a silicon nitride film with a film thickness of 1 to 4 nm, protrusions can be formed and enlarged on the surface of the silicon nitride film on the protrusion-like defects, and deterioration of roughness and haze caused by the formation of the silicon nitride film can be suppressed. Therefore, based on the size of the detected protrusions, the size of smaller protrusion-like defects can be estimated.

[0015] In addition, in the defect inspection method of the present invention, in the silicon nitride film forming step, it is preferable that the forming temperature of the silicon nitride film is 500°C or higher and 580°C or lower.

[0016] With such a temperature range, a silicon nitride film with more suppressed haze deterioration can be formed.

[0017] In addition, in the defect inspection method of the present invention, the relationship between the preset film thickness of the silicon nitride film and the amount of enlargement of the detected size is preferably set based on the change amount of the detected size before and after the formation of the silicon nitride film detected on another substrate in advance.

[0018] There is a correlation between the detected sizes before and after the formation of the silicon nitride film in an appropriate film thickness range (1 to 4 nm), and the detected size after the formation of the silicon nitride film increases as the film thickness increases (that is, the amount of enlargement increases). Therefore, it is easy to set the relationship between the film thickness and the amount of enlargement of the detected size based on the change amount of the detected size before and after the formation of the silicon nitride film obtained on another substrate in advance. Therefore, from the size of the protrusions detected after the formation of the silicon nitride film and the relationship between the preset film thickness of the silicon nitride film and the amount of enlargement of the detected size, the size of the protrusion-like defects before the formation of the silicon nitride film can be easily estimated.

[0019] In addition, in the defect inspection method of the present invention, in the detection step, it is preferable that the measurement sensitivity during detection by the surface inspection device is higher than 19 nm.

[0020] With such measurement sensitivity, it is possible to detect the size of small protrusions that cannot be detected at the measurement sensitivity of 19 nm of a general surface inspection apparatus, and based on the size of the detected protrusions, it is possible to estimate the size of smaller protrusion-like defects.

[0021] Further, in the defect inspection method of the present invention, it is preferable that the size of the protrusion-like defect before the formation of the silicon nitride film is less than 10.6 nm.

[0022] Such protrusion-like defects smaller than 10.6 nm are smaller than the minimum sensitivity of the latest particle counter, which is a typical surface inspection apparatus, so the size of the protrusion-like defects could not be estimated by the conventional method. However, by the means of the present invention described above, it is possible to estimate the size of even smaller protrusion-like defects.

Advantages of the Invention

[0023] In the defect inspection method of the present invention, by forming a silicon nitride film with a thickness of 1 to 4 nm, it is possible to expand and form protrusions on the surface of the silicon nitride film on the protrusion-like defects, and it is possible to suppress the deterioration of roughness and the deterioration of haze caused by roughness due to the formation of the silicon nitride film. Therefore, based on the size of the detected protrusions, it is possible to estimate the size of smaller protrusion-like defects. Specifically, it is possible to detect the size of protrusion-like defects smaller than the minimum sensitivity (10.6 nm) of the latest particle counter, which is a typical surface inspection apparatus.

Brief Description of the Drawings

[0024]

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Embodiments for Carrying Out the Invention

[0025] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0026] As described above, there has been a demand for providing a defect inspection method capable of detecting the size of smaller protrusion-like defects.

[0027] The inventors of the present invention have intensively studied the above problems, and even in the case of measuring with a high-sensitivity particle counter, they have focused on examining whether there is a method capable of measuring minute protrusion-like defects with higher sensitivity by utilizing the lens effect due to the formation of the nitride film.

[0028] Conventionally, it has been known that when particles are coated with a CVD film such as a silicon nitride film, their size increases and they become easier to detect. By utilizing this, high-sensitivity measurement should originally be achievable. And the reason for the decrease in sensitivity after CVD film formation is the haze deterioration caused by CVD. Therefore, it was thought that high sensitivity could be achieved by using thin-film CVD that enlarges small defects slightly without causing haze deterioration. Currently, the minimum sensitivity of a particle counter is about 10 nm, the scattered light intensity used for detection is very weak, and it is very difficult to further improve the sensitivity by several nm from a 10-nm size with the improvement of the particle counter. However, in the research by the present inventors, by forming a nitride film with a thickness of several nm, the particles are coated with several nm to enlarge them, and finally, defects smaller than 10 nm by several nm can be detected.

[0029] Looking back, in the conventional method, for defects with a size of 12 nm or more, the effect of increasing the particle size was greater than the sensitivity deterioration due to haze caused by the formation of the CVD film. Therefore, high sensitivity could be achieved by forming the CVD film. However, for defects with a size of around 10 nm, the increase in size due to the formation of the CVD film was small, and rather, due to the haze deterioration, the defects became invisible. This time, by performing thin-film CVD, it was possible to enlarge and detect defects with a size of 10 nm or less while maintaining a state with little haze deterioration. As a result, it became possible to detect defects smaller than the sensitivity of the latest particle counter.

[0030] In this way, the present inventors found a method capable of measuring minute protrusion-like defects with higher sensitivity and completed the present invention.

[0031] That is, the defect inspection method of the present invention includes a silicon nitride film forming step of forming a silicon nitride film with a thickness of 1 to 4 nm on the substrate in order to enlarge the detection size of the protrusion-like defects existing on the surface of the substrate, a detection step of detecting the size of the protrusions enlarged and formed on the surface of the silicon nitride film on the protrusion-like defects with a surface inspection device after the silicon nitride film forming step, and a defect size estimation step of estimating the size of the protrusion-like defects before the formation of the silicon nitride film from the relationship between the size of the protrusions detected in the detection step, the preset thickness of the silicon nitride film, and the amount of enlargement of the detection size.

[0032] Hereinafter, the present invention will be described in detail with reference to the drawings as an example of an embodiment, but the present invention is not limited thereto.

[0033] FIG. 1 is a flowchart showing an example of the defect inspection method of the present invention.

[0034] <Step S1: Silicon nitride film forming step> Step S1 is a step of forming a silicon nitride film with a thickness of 1 to 4 nm on the substrate in order to enlarge the detection size of the protrusion-like defects existing on the surface of the substrate.

[0035] Conventionally, when the film thickness is several tens of nm, by deliberately making a thin film of 1 to 4 nm, protrusions can be enlarged and formed on the surface of the silicon nitride film on the protrusion-like defects, and deterioration of roughness and haze deterioration caused by roughness due to the formation of the silicon nitride film can be suppressed.

[0036] Here, the formation temperature of the silicon nitride film is preferably 500°C or higher and 580°C or lower. With such a temperature range, a silicon nitride film with more suppressed haze deterioration can be formed.

[0037] <Step S2: Detection step> Step S2 is a step of detecting the size of the protrusions enlarged and formed on the surface of the silicon nitride film on the protrusion-like defects with a surface inspection device after the silicon nitride film forming step of Step S1.

[0038] The particle counter used as the surface inspection device is not particularly limited as long as it can detect defects (in this case, protrusions), measure the number of defects, and measure the defect size. For example, a commercially available one can be used, such as the SP7 manufactured by KLA-Tencor. Using such a particle counter, an LPD (Light Point Defect) map, that is, the defect distribution within the wafer surface, is obtained.

[0039] By obtaining such an LPD map, the number of defects (and their position coordinates (also simply referred to as coordinates)) existing within the wafer surface can be measured. At the same time, by adjusting the detection sensitivity and setting the level of the defect size to be detected, it is possible to measure, together with each position coordinate, how many defects of a predetermined defect size exist within the plane. The adjustment of the detection sensitivity can be determined each time according to the required defect size. The detection sensitivity can be, for example, a general 19 nm or the highest sensitivity of the SP7, which is 10.6 nm. The defect size can be measured from the size of the LPD.

[0040] In addition, as will be described later, measurements are also performed after forming the nitride film, and by comparing based on the coordinates of each defect within the wafer surface at each measurement, together with information on each defect size, for example, the number of defects detected in the measurement before forming the nitride film, the number of defects detected at the same position as in the measurement before forming the nitride film in the measurement after forming the nitride film, the number of defects detected in the measurement before forming the nitride film but not detected at the same position in the measurement after forming the nitride film, the number of defects newly detected in the measurement after forming the nitride film, and other various data regarding the number of defects can be obtained.

[0041] In addition, in the detection step of step S2, it is preferable that the measurement sensitivity during detection by the surface inspection apparatus is higher than 19 nm. With such a measurement sensitivity, it is possible to detect the size of small protrusions that cannot be detected at a measurement sensitivity of 19 nm of a general surface inspection apparatus, and based on the size of the detected protrusions, it is possible to measure by estimating the size of smaller protrusion-like defects.

[0042] Furthermore, it is preferable that the size of the protrusion-like defect before forming the silicon nitride film is less than 10.6 nm. Such protrusion-like defects less than 10.6 nm are smaller than 10.6 nm, which is the minimum sensitivity of the latest particle counter, so the size of the protrusion-like defects could not be measured by the conventional method. However, in the embodiment of the present invention, it is possible to estimate and measure even the size of smaller protrusion-like defects.

[0043] <Step S3: Defect Size Estimation Step> Step S3 is a step of estimating the size of the protrusion-like defect before forming the silicon nitride film from the size of the protrusion detected in the detection step of step S2 and the relationship between the preset film thickness of the silicon nitride film and the amount of increase in the detection size.

[0044] The relationship between the preset film thickness of the silicon nitride film and the amount of increase in the detection size is preferably set based on the amount of change in the detection size before and after forming the silicon nitride film detected on another substrate in advance.

[0045] There is a correlation between the detection sizes before and after forming the silicon nitride film in an appropriate film thickness range (1 to 4 nm), and the detection size after forming the silicon nitride film increases as the film thickness increases (that is, the amount of increase becomes larger). Therefore, it is easy to set the relationship between the film thickness and the amount of increase in the detection size based on the amount of change in the detection size before and after forming the silicon nitride film obtained on another substrate in advance. Therefore, from the size of the protrusion detected after forming the silicon nitride film and the relationship between the preset film thickness of the silicon nitride film and the amount of increase in the detection size, the size of the protrusion-like defect before forming the silicon nitride film can be easily estimated.

[0046] Next, based on an example of the above defect inspection method, the size of small protrusion-like defects is estimated, and a comparison with the estimation result by the conventional method is attempted.

[0047] First, as a conventional method, in Patent Document 1, a nitride film with a thickness of several tens of nm for enlarging particles was formed. Following this, in FIG. 2, an example of forming a 50-nm-thick nitride film at 750°C is shown. Here, FIG. 2 is an LPD map before and after forming a silicon nitride film with a thickness of 50 nm. FIG. 2(a) is the result of measuring particles before nitridation with a detection sensitivity of 15 nm, and FIG. 2(b) is the result of measuring particles after nitridation with a detection sensitivity of 19 nm.

[0048] In this case, the size of the particles was enlarged due to the formation of the nitride film. In the measurement with a detection sensitivity of 19 nm after nitridation, in addition to the defects detected with a detection sensitivity of 15 nm before nitridation, new defects were detected. That is, smaller defects were detected by the formation of the nitride film.

[0049] On the other hand, when the nitride film is formed, although the particle size increases, at the same time, the haze becomes worse. When a 50-nm film is formed, the detection sensitivity of the minimum size after film formation becomes 19 nm. Measurement at a detection sensitivity of 18 nm could not measure the particles due to the influence of haze.

[0050] As a result of the above experiment, it was found that the particles whose size expands to 19 nm due to the formation of a 50-nm nitride film are particles with an original size of about 12 nm. That is, particles with a size of 12 nm or less before nitridation do not expand to a size of 19 nm or more even when a 50-nm nitride film is formed. Therefore, they will not be detected after nitridation by a particle counter with a maximum sensitivity of 19 nm.

[0051] Since the maximum sensitivity of recent particle counters is about 10 nm, defects smaller than 12 nm can be measured by the latest particle counters without forming a nitride film, and if a nitride film is formed, they cannot be measured due to the influence of haze.

[0052] Figure 3 shows the LPD maps before and after the formation of a silicon nitride film with a thickness of 50 nm. Figure 3(a) shows the measurement results with a detection sensitivity of 12.5 nm before nitridation, Figure 3(b) shows the measurement results with a detection sensitivity of 10.6 nm before nitridation, and Figure 3(c) shows the measurement results with a detection sensitivity of 19 nm after nitridation.

[0053] When comparing the number of defects before and after the formation of the nitride film, the number of defects with a detection sensitivity of 10.6 nm before the formation of the nitride film is much larger than that with a detection sensitivity of 19 nm after the formation of the 50-nm nitride film. Also, when comparing the detection sensitivity of 12.5 nm before the formation of the nitride film and 19 nm after the formation of the nitride film, the difference in the number of defects is such that the number of defects with a detection sensitivity of 12.5 nm before the formation of the nitride film is slightly less. Therefore, it was estimated that a detection sensitivity of about 12 nm before the formation of the nitride film corresponds to a detection sensitivity of 19 nm after the formation of the nitride film.

[0054] To increase the detection sensitivity of particles after the formation of the nitride film, it is necessary to make the defects larger during the formation of the nitride film and suppress the deterioration of haze due to nitridation. Therefore, as a result of intensive studies on methods to achieve this, it was found that the above problems can be solved by reducing the thickness of the nitride film. Specifically, it is necessary to set the film thickness to 1 nm to 4 nm.

[0055] It was also found that it is more preferable to lower the formation temperature of the nitride film. Specifically, it is more preferable to set the nitride film formation temperature to 500 °C to 580 °C.

Example

[0056] Hereinafter, the present invention will be described more specifically by showing examples of the present invention, but the present invention is not limited thereto.

[0057] (Example 1, Comparative Example 1) The difference in the detection sensitivity of defects due to the formation of a nitride film was compared between the case of forming a nitride film with a nitride film thickness of 50 nm and a nitride film formation temperature of 750 °C on a 300-mm diameter substrate (Comparative Example 1) and the case of forming a nitride film with a nitride film thickness of 4 nm and a nitride film formation temperature of 630 °C (Example 1).

[0058] The particle counter is an SP7xp manufactured by KLA-Tencor (the highest sensitivity is 10.6 nm). The nitride film was formed from SiH2Cl2 and NH3 to form a Si3N4 film. The measurement sensitivity of the SP7xp before forming the nitride film was set to 10.6 nm.

[0059] The following shows a comparison of the defect maps before and after forming the nitride film. Figure 4 is an LPD map comparing the differences in film thickness and measurement sensitivity. The upper row is Comparative Example 1, and the lower row is Example 1. Horizontally, it shows the results according to whether it is before or after nitridation and the difference in each detection sensitivity (also referred to as measurement sensitivity).

[0060] (Comparative Example 1) In the formation of a 50-nm nitride film, the number of defects is less for the detection sensitivity of 19 nm after forming the nitride film compared to the result of the detection sensitivity of 10.6 nm before forming the nitride film. The detection sensitivity decreases by forming the nitride film.

[0061] Also, when the measurement after forming the nitride film was performed at a detection sensitivity of 15 nm, it overflowed and could not be measured due to the haze deterioration caused by forming the nitride film.

[0062] (Example 1) When the film thickness is reduced to 4 nm (the nitride film formation temperature is 630 °C), it becomes possible to measure up to a measurement sensitivity of 15 nm after nitridation. At the same time, a new defect flow pattern can be seen near the position at the 6 o'clock direction (downward) of the substrate on the paper surface.

[0063] For a 4-nm nitride film, the measurement at a detection sensitivity of 13 nm could not be measured due to overflow caused by haze deterioration. Even when forming a thin nitride film, the haze on the substrate surface becomes worse, so high-sensitivity measurement with a detection sensitivity of 10.6 nm that could be measured before forming the nitride film could not be performed.

[0064] Regarding the flow pattern of defects in the 6 o'clock direction (downward) on the paper surface that occurred at a detection sensitivity of 15 nm, this substrate was contaminated from the brush part of the substrate transfer BOX. Due to the influence of the contamination, micro-particles with a size of 10.6 nm or less adhered, and it is considered that the size of the protrusions increased during the subsequent nitride film formation and became detectable. That is, by reducing the thickness of the nitride film, which is a necessary condition, the deterioration of haze can be suppressed, and even when measured with a high-sensitivity particle counter with a maximum sensitivity of 10.6 nm, it was found that a measurement with a higher sensitivity than 10.6 nm (i.e., the size of smaller protrusion-like defects can be estimated) is possible due to the formation of the nitride film.

[0065] Next, it will be explained how the particle size changes during the formation of the nitride film. In this case, defects that were not detected before the formation of the nitride film are detected after the formation of the nitride film, realizing high-sensitivity measurement. A method for assuming the original size before the formation of the nitride film from the detection size after the formation of the nitride film will be shown.

[0066] The positions of the particles detected before and after the formation of the nitride film are compared below. Figure 5 is an LPD map before and after the formation of a 4-nm-thick silicon nitride film. Figure 5 shows the results when measured at a measurement sensitivity of 10.6 nm before the formation of the nitride film and when measured at a measurement sensitivity of 14 nm after the formation of a 4-nm-thick nitride film at 580 °C. It can be seen that there are a large number of defects newly detected due to the formation of the nitride film.

[0067] In the figure, the points indicated by triangles are the defects commonly observed before and after the formation of the nitride film. When examining the size change of this defect before and after the formation of the nitride film, it became as shown in Figure 6. Figure 6 is a graph of the defect size change before and after the formation of a 4-nm-thick silicon nitride film. An average size increase of 5.9 nm was observed. However, not all of them became 5.9 nm larger. There were some that became more than 10 nm larger, and there were also some defects that did not change much. Using this relationship, it becomes possible to estimate the approximate original size.

[0068] The particle size distribution after nitridation at this time is shown in Fig. 7. Among the defects indicated by the □ symbol on the defect map of Fig. 5, which occurred after the formation of the nitride film but not before, there are many defects in the 14 nm range, and it can be seen that there are also many 14 nm particles in Fig. 7. Considering that the detection sensitivity was 10.6 nm before nitridation and no defects were detected, and the average size increased by about 5.9 nm, it can be estimated that the defects with a size of approximately 9 - 10.6 nm before the formation of the nitride film grew to 14 nm due to the size increase caused by the nitride film.

[0069] (Comparative Example 2) Next, Fig. 8 shows what kind of defect size changes occurred before and after the formation of nitride films with a thickness of 6 nm at 610 °C and 9.5 nm at 600 °C. Fig. 8(a) shows that the size increased by an average of 7.4 nm when forming a nitride film with a thickness of 6 nm, and Fig. 8(b) shows that the size increased by an average of 14 nm when forming a nitride film with a thickness of 9.5 nm. However, the variation in the amount of size increase for each individual case was large, and it was found that it was difficult to estimate the original size before the formation of the nitride film from the detected size after the formation of the nitride film. (The measurement sensitivity of SP7xp after the formation of the nitride film at this time was 15 nm.)

[0070] (Comparative Example 3) Next, Fig. 9 shows the state of size change when forming a thin nitride film with a thickness of 0.4 nm. When forming a nitride film with a thickness of 0.4 nm at 500 °C (forming the nitride film in a shorter time than when forming a film with a thickness of 1.2 nm), no size change was observed before and after the formation of the nitride film. At this time, although it was possible to measure with a measurement sensitivity of 10.6 nm even after the formation of the nitride film, since the size did not increase, the result was that no increase in sensitivity could be expected even when forming the nitride film.

[0071] (Example 2) Therefore, when a nitride film with a thickness of 1.2 nm, which is intermediate between Comparative Example 2 and Comparative Example 3, was formed at 500°C, it was possible to measure at a measurement sensitivity of 10.6 nm even after the formation of the nitride film. Moreover, as shown in the LPD map of FIG. 10, new defects were detected. As shown in the defect size change graph of FIG. 11, it was estimated that the size increased by 1.5 nm due to the formation of the nitride film, and it was found that the variation in the size increase amount was small. Therefore, it can be estimated that the original size of the newly generated defects is 9 to 10.6 nm. FIG. 12 is a graph showing the particle size distribution after the formation of a silicon nitride film with a thickness of 1.2 nm, and a large number of particles with small sizes are observed.

[0072] The film thickness, the SP7 measurement size before the formation of the nitride film, the SP7 measurement size after the formation of the nitride film, and the size increase amount shown in the above Examples 1 and 2 and Comparative Examples 2 and 3 were summarized and arranged in ascending order of film thickness in Table 1. Also, the size before nitridation was estimated under each condition.

[0073]

Table 1

[0074] Among these, for a film thickness of 0.4 nm (Comparative Example 3), although the variation in the size increase amount is small, the size of the protruding defects less than 10.6 nm cannot be estimated. For film thicknesses of 6 nm and 9.5 nm (both Comparative Example 2), since the variation in the size increase amount is large, even if an attempt is made to calculate the size before nitridation, the accuracy is poor, and the size of the protruding defects less than 10.6 nm cannot be accurately estimated.

[0075] The film thicknesses for which the variation in the size increase amount is small and the size of the protruding defects less than 10.6 nm can be estimated are 1.2 nm (Example 2) and 4 nm (Example 1). Also, the estimated values of the size before nitridation for each are 9.1 nm and 8.1 nm, respectively, and it was found that the size of the protruding defects smaller than the minimum sensitivity (10.6 nm) of the latest particle counter can be estimated. Table 1 above summarizes the results of these Examples 1 and 2 and Comparative Examples 1 to 3.

[0076] Furthermore, a size increase of 5.9 nm can be achieved by forming a silicon nitride film with a thickness of 4 nm (Example 1), and a size increase of 1.5 nm can be achieved by forming a silicon nitride film with a thickness of 1.2 nm (Example 2). When this is applied to the formula in Patent Document 1 where the film thickness ≥ (inspection apparatus detection sensitivity - defect size) × safety factor and the safety factor = 100%, in the case of an inspection apparatus detection sensitivity of 14 nm and an original defect size of 8.1 nm in Example 1, it is necessary to have a silicon nitride film thickness > 5.9 nm, and the actual film thickness of 4 nm in Example 1 is not included. Similarly, in the case of an inspection apparatus detection sensitivity of 10.6 nm and an original defect size of 9.1 nm in Example 2, it is necessary to have a silicon nitride film thickness > 1.5 nm, and the actual film thickness of 1.2 nm in Example 2 is not included. That is, Examples 1 and 2 of the present invention are not included in the scope of Patent Document 1.

[0077] Thus, when inspecting protrusion-shaped defects, the present invention can suppress variations due to deterioration of roughness and haze deterioration caused by roughness by forming a thinner silicon nitride film (film thickness 1 - 4 nm) different from the scope of Patent Document 1, and can estimate the size of protrusion-shaped defects smaller than the minimum sensitivity (10.6 nm) of the latest particle counter.

[0078] The present invention includes the following aspects. [1]: A silicon nitride film forming step of forming a silicon nitride film with a thickness of 1 - 4 nm on the substrate in order to enlarge the detection size of protrusion-shaped defects existing on the surface of the substrate; A detection step of detecting, with a surface inspection apparatus, the size of a protrusion portion formed by enlargement on the surface of the silicon nitride film on the protrusion-shaped defect after the silicon nitride film forming step; A defect size estimation step of estimating the size of the protrusion-shaped defect before the formation of the silicon nitride film from the relationship between the size of the protrusion portion detected in the detection step, the preset film thickness of the silicon nitride film, and the amount of enlargement of the detection size; A defect inspection method characterized by including the above. [2]: The defect inspection method according to [1] above, wherein in the silicon nitride film forming step, the formation temperature of the silicon nitride film is 500°C or higher and 580°C or lower. [3]: The relationship between the thickness of the pre-set silicon nitride film and the enlarged amount of the detection size is set based on the change amount of the detection size before and after the formation of the silicon nitride film detected on another substrate in advance, and is characterized in that it is the defect inspection method according to [1] or [2] above. [4]: In the detection step, the measurement sensitivity during detection by the surface inspection device is set to be higher than 19 nm, and is characterized in that it is the defect inspection method according to any one of [1] to [3] above. [5]: The size of the protrusion defect before the formation of the silicon nitride film is less than 10.6 nm, and is characterized in that it is the defect inspection method according to any one of [1] to [4] above.

[0079] Note that the present invention is not limited to the above embodiments. The above embodiments are examples, and those having substantially the same configuration as the technical idea described in the claims of the present invention and exhibiting the same operational effects are included in the technical scope of the present invention regardless of what they are.

Explanation of symbols

[0080] S1, S2, S3... steps.

Claims

1. A silicon nitride film forming step of forming a silicon nitride film with a film thickness of 1 to 4 nm on the substrate in order to enlarge the detection size of the protruding defects existing on the surface of the substrate; A detection step of detecting, with a surface inspection device, the size of the protrusions formed by expanding on the surface of the silicon nitride film on the protruding defects after the silicon nitride film forming step; A defect size estimation step of estimating the size of the protruding defects before the formation of the silicon nitride film from the relationship between the size of the protrusions detected in the detection step, the preset film thickness of the silicon nitride film, and the amount of expansion of the detection size; A defect inspection method, characterized by including the above.

2. The defect inspection method according to claim 1, characterized in that in the silicon nitride film forming step, the formation temperature of the silicon nitride film is 500°C or higher and 580°C or lower.

3. The defect inspection method according to claim 1 or 2, characterized in that the relationship between the preset film thickness of the silicon nitride film and the amount of expansion of the detection size is set based on the amount of change in the detection size before and after the formation of the silicon nitride film detected on another substrate in advance.

4. The defect inspection method according to claim 1 or 2, characterized in that in the detection step, the measurement sensitivity during detection by the surface inspection device is made higher than 19 nm.

5. The defect inspection method according to claim 1 or 2, characterized in that the size of the protruding defects before the formation of the silicon nitride film is less than 10.6 nm.

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